Many chemical analytical instruments rely upon controlled and accurate fluid flow through the instrument during analytical processing. Such instruments include machines designed to perform chemical analysis of various types, purify samples and to perform monitoring of various aspects of laboratory and commercial processing. To name just a few of the types of analytical instruments in which precise fluid flow is a critical part of the functioning of the machines, there are chromatographs of numerous types such as gas chromatographs (GCs) and liquid chromatographs (LCs), spectrophotometers of many kinds, and many other similar instruments. Gas chromatographs, for example, rely upon accurate control and processing of known quantities of gas flowing through separation columns during the analytical processing. The accuracy and precision of analytical results depend directly on accurate and precise fluid flow. Accordingly, without accurate control of fluid flow, analytical results are compromised.
In a GC the sample is in the form of gas. Samples of fluid under test are typically under the control of control devices such as pumps, valves, pressure transducers and pressure regulators. The control devices help in the acquisition of samples, and the isolation, handling and separation of the samples during the process of chemical analysis. In a chromatograph, a sample aliquot is directed, either manually or automatically, through a complicated array of plumbing hardware and control systems that perform various functions before the sample flows through one or more separation columns and detectors. In the separation columns different compounds in the sample fluid are isolated as a result of specific physico-chemical interactions with the separation materials contained within the column while under flow. As the isolated compounds flow out of the columns they flow through detectors of various kinds that assist in identifying and quantifying the compounds.
In a chromatograph the fluid flow and control systems must accommodate several other fluids in addition to sample fluids. These include carrier and calibration fluids, which must be routed in very specific precisely and accurately controlled flow paths through the instrument.
It is obvious that in many analytical instruments that require controlled fluid flow there are numerous fluid flow paths, and complex hardware systems that include tubing, couplings, valves, sensors, pumps and regulators of various kinds. The plumbing systems in even relatively simple instruments such as some chromatographs can become exceedingly complicated, not to mention the complexity added by the fluid control systems.
There are a variety of different kinds of valves used in analytical instruments such as chromatographs in order to direct and control fluid flow. Among these are binary valves, rotary valves, and slide valves, and combinations of these. In addition, there are multiple binary valves such as two and three-way binaries, which may be connected in various combinations to simultaneously direct fluid flow through single or multiple flow channels. Rotary valves, diaphragm valves and slide valves, both dual and multi-position, are used to direct fluid flow through multiple ports and channels that are arranged in either a circular or linear orientation.
Precision, reliability, repeatability, reproducibility and accuracy are of course primary goals of any such analysis. As such, it is essential in an analytical instrument to eliminate, or at least minimize, all sources of system failure that may detract from these goals or might lead to problems such as leaking fittings that can adversely effect the analytical processing. The complexity of the plumbing and fluid controlling hardware of many analytical instruments presents a situation that is at odds with the fundamental principles of accuracy and precision that such instruments rely upon. Accurate precise, repeatable and reproducible analytical results require correspondingly accurate, precise, repeatable and reproducible fluid processing, without system failures such as non-fluid-tight couplings. But every fitting, connection, interconnection and fluid-controlling device in an analytical instrument introduces a potential site for a problem such as a leak. When even a small leak occurs in a critical connection the accuracy, precision, repeatability and reproducibility of analytical test data is compromised. In an instrument that contains dozens of couplings and connections the opportunity for incorrectly connected fittings is multiplied many times over.
The problems described above with respect to complicated fluid connections are well known to any laboratory technician who has operated an analytical instrument such as those described. Even in the relatively idealized conditions of a modern laboratory, and even with laboratory grade instruments, plumbing problems are a constant source of trouble with analytical instruments such as chromatographs. As such, there is a great benefit in reducing the number and complexity of fittings in an instrument that uses fluid flow.
But the problems noted above are even more pronounced with analytical instruments that are designed for use in the field rather than in a controlled laboratory environment. There are several reasons. First, field instruments tend to be smaller since portability may be a primary goal. As the instruments get smaller so do the fittings and connections. Miniaturized hardware mandates reduced fluid flow rates, and it becomes correspondingly difficult to ensure fluid-tight processing. Second, an instrument designed for use in the field is often subject to more extreme environmental conditions and rougher handling. In many respects, therefore, field units need to be even more robust than their laboratory counterparts. This can be a difficult objective when another goal in designing the unit is reduction of size.
The problems described above with complicated plumbing, control and hardware systems are amplified many times over under field conditions of extreme hot or cold environments. Extreme temperature variations can cause thermal expansion and contraction that leads to leaking fittings and other connections. In addition, environmental vibrations can, over time, loosen fittings and damage sensitive connections.
Therefore, despite advances in the technological solutions surrounding analytical instruments designed to sample, analyze and report data from remote locations, there is a need for a fluid handling system that is rugged and redundant enough that it will function without failure and without regular maintenance. There is a further need for a fluid handling system that uses small quantities of fluid so that it may be used with miniaturized instruments. Such a fluid handling system would be advantageously and beneficially used in both field instruments and in laboratory grade instruments.
The present invention relates a multiport rotary valve that in a preferred embodiment has six separate external ports. The valve simplifies fluid handling systems by replacing a relatively large number of individual two and three-way binary valves or conventional rotary valves that would be required to do the same fluid handling. The invention greatly reduces the number of active components in the fluid handling system, including tubing, fittings, junctions, etc., and thereby decreases the number of possible failure points—i.e., leaks, mechanical and electrical failure points. The rotary valve of the present invention improves reliability and provides positive positional feedback that greatly improves error and failure detection, and the valve reduces material assembly costs. Finally, the valve according to the present invention minimizes interconnecting volumes between system components, which minimizes the amount of fluid cross-contamination and mixing between various components of the system. This improves both accuracy and precision of analytical results.